


Bonding With The Mad King

by HimeBee



Category: Fate/Grand Order
Genre: Biting, Cowgirl Position, Creampie, Established Relationship, F/M, Fluff, Fluff and Smut, Kissing, Knotting, Love Confessions, Marking, Overstimulation, Possessive Behavior, Scent Kink, Sexual Tension, Sleepy Sex, Teasing
Language: English
Status: Completed
Published: 2019-07-17
Updated: 2019-07-29
Packaged: 2020-06-29 21:12:15
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,675
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19838590
Author URL: https://archiveofourown.org/users/HimeBee/pseuds/HimeBee
Summary: The summoning and bonds between a Master, and her newly summoned Berserker Servant.





	1. Bonds 0-9

**Author's Note:**

  * For [SylvaneVentus](https://archiveofourown.org/users/SylvaneVentus/gifts).

**Summary for the Chapter:**

> You summon and bond with Cu Chulainn (Alter).

**Notes for the Chapter:**

> ★ I mainly wrote this for my friend, Syl to make her feel a bit better .3.
> 
> ☆ I made it a reader-insert though, so others could enjoy it uvu Even still, I hope it's sufficient! 
> 
> [Bond 10 will have a chapter all to its self for some nice, spicy smut!]

**The Summoning:**

* * *

Your first time summoning Cu Chulainn as a Berserker class Servant was nothing short of jarring and extremely awkward. His imposing figure had startled you greatly to the point where your knees gave out and you fell to the ground before him, staring up at your newly summoned Servant with a bemused expression.

“Cu Chulainn. Answering your summon, I’ve arrived.” His deep voice caused you to shiver throughout your whole body as you stayed rooted in the same spot on the floor; nonchalance painted his features as he finally regarded you; his Master possibly.

“...I take it you are my Master.” He didn’t exactly sound ecstatic about this.

“Oi, stand up. You're small enough and I’m having difficulties seeing you already. Don't make yourself even harder to see.” You nodded before standing to your feet, albeit very shakily. You attempted to offer him a disarming smile, but he still didn’t look pleased in the slightest.

“Y-yes, I am your Master.” You cursed your voice for trembling as much as it did, and yet you couldn’t help it. He was actually a bit scary…

"You are very tiny for a Master.” His blasé words caused a disgruntled pout to appear on your face, hands flying to your hips in retaliation.

“I may be tiny, b-but you still have to obey me!” Those crimson-red eyes of his sized you up slowly, starting from your feet and trailing up to your face. You felt oddly exposed all of a sudden...

“Tch, whatever.” Berserker brushed past you as he walked away, ignoring your exasperated shouts after him.

_“Waaaittt!”_

**Bond Level: 0**

* * *

After the summoning, you attempted to make conversation with Cu Alter. He ignored you, for the most part, and it ticked off your other Cu’s greatly.

“Wow, what a jerk.” Prototype Cu snarled, making a spitting gesture at his back as Alter walked down the hall.

“How do you put up with someone like that, Master? I’ll be the first to admit that I’m not exactly the most open Servant, but I could never ignore a pretty little lady asking for my help.” Lancer grinned as he put his arm around you, pulling you closer to his body. You laughed as you hit his chest playfully.

“He just got here, so try to at least be civil, guys. After all, he _is_ you and at the same time he isn’t, so I’m sure we’ll get along eventually.” Caster sighed as he watched Lancer nuzzling against you. Alter was no longer in the hallway when he turned back around.

“I have a feeling he doesn’t exactly want to be civil with us, Master...”

**Bond Level: 1**

* * *

Eventually, Chaldea set up a room for your newly summoned Berserker class Servant. As usual, his expression did not betray his actual emotions in the slightest. He appeared to be just as uninterested when you first summoned him. Nevertheless, you decided to pay him a visit, just to see if he was settling in well enough

You knocked on his door a few times and waited outside the room, hearing a few shuffles within before the door swung open; narrowly missing your face. Despite nearly being hit by the door, possibly on purpose, you offered him a smile. But you couldn’t think of what to say to someone like him.

“Um, hi. Are you settling in alright? I just wanted to check up on you.” Cu stared at you for a few moments before you saw his hand moving to shut the door on you again. Without thinking, you put your foot in the way to stop it from shutting fully.

“W-wait, Cu-!” Berserker looked annoyed, eyeing your foot stuck in the door before shifting his gaze back up to your expectant face. Why were you here? 

“It’s unnecessary for you to check up on me as if I'm some brat,” he opened the door all the way, only to block the entrance into his room with his body. Your eyes become fixated on that malevolent smirk, full of sharp teeth, suddenly replacing the straight-face he ascertained most of the time.

“...Don’t stand before me without any defenses, Chaldea Master. I just might gut you without thinking.” That being said, he shut the door in your face with a loud thud.

You suddenly felt as if all the peppy energy had been drained from your body.

**Bond Level: 2**

* * *

After your exchange with Cu Alter the other day, you felt very discouraged. He was extremely different from your other loving Cu's. Perhaps you wouldn't get along after all…

"Your orders have been lacking in battle. What's the matter with you." It wasn't exactly a question bred from concern, but at least he cared enough to ask anyways.

"Oh, nothing. I'm just tired is all." The Berserker Servant eyed you suspiciously before kneeling down by your side whilst you enjoyed a cup of coffee on the plush sofa. Well, you _were_ enjoying it until the memories of yesterday began plaguing your thoughts. He had upset you.

"...Don't think too much about a Servant's personality." Your attention snapped to him, but Cu was facing forward and not looking at you as he spoke.

"In the end we are weapons, and if needed, we can become enemies at any moment." The porcelain mug you were holding began to shake along with the trembling of your fingers wrapped around its handle.

"W-why are you telling me this?" Cu sensed your state of tumult after your talk the other day, however he wasn't sure what to say to get your bubbly personality back. It perturbed him, not that he was willing to admit that aloud of course.

"Because I-- your other Servants don't need you worrying about such trivial things. They trust you and expect you to lead them correctly. Don't misuse that trust, Chaldea Master." Cu stood up then, turned around and walked away without sparing a look in your direction again.

You sat there in the same spot where he found you, too shocked to move at all aside from staring wordlessly into your cup of swirling coffee. Oddly enough, you felt a tiny bit closer to him now…

**Bond Level: 3**

* * *

You were beginning to feel a bit better now, it being a few weeks since you first summoned Cu Alter. Later that day, Lancer Cu invited you to have a drink with him and the other Cu's and of course you accepted, even if you had no intention of getting drunk. It was nice to hang out with your Servants and socialize every now and then.

After a few drinks, Lancer was a bit tipsy and in the middle of telling a hilarious story about being rejected by a cute girl. The other Cu's were laughing along with him, when you spotted Alter walking down the hallway.

"Hey, Berserker! Come join us!" The Cu's all went silent when they saw Alter, all laughter and merriment ceasing immediately. You weren't deterred in the slightest, however.

"No thanks." You pouted before excusing yourself, assuring them you would be back soon. Caster patted your head, a sad smile crossing his lips.

"I understand you just want to get along with your Servants, but some are just not the sociable type, Master." You returned his smile, expression pained yet hopeful.

"I still have to try, Caster." Alter couldn't have gotten far at the slow pace he was walking, so it should be easy to catch up with him. 

That was apparently not so, considering you ended up having to run after him.

"Berserker, wait!" He peered over his shoulder to see you practically sprinting toward him. It was quite amusing.

"You should go back and enjoy yourself. I'm more than certain they make better companions than me." You shook your head in denial, hands on your knees as you struggled to catch your breath.

"I.. I don't compare my friends' personalities or abilities. Everyone is so different, so it wouldn't be fair." Friends? Had you said "friends" and not "Servants"?

"Even still, I don't think I could ever act the way they do… Not that I'm envious or anything like that." He turned around to fully face you, head tilted slightly upwards so that he was looking down at you with his nose turned up.

"...You look tired. Make sure you don't stay up too late with your Servants. Tomorrow is a day for battle, Master." With that being said, your Servant continued on his way down the hall, walking away from you once again.

Wait… Had he called you "Master" instead of “Chaldea Master”?

**Bond Level: 4**

* * *

You visited Cu Alter in his room a few days later to ask him about things he liked and disliked. It was mostly a one-sided conversation, but you were still pleased when he even allowed you into his room.

He stood with his arms crossed, back against the wall as he listened to you talk. Whenever you asked a question, he would give curt responses. But that didn't seem to deter you even one bit. You continued talking, not that he hated it at this point…

"Things you hate?" Cu pondered the question for a few moments, his eyes now opened and focused on the ceiling.

"I don't exactly hate my enemies, I just kill them. There's no dishonesty there..." Your heart skipped a beat when his eyes suddenly focused on you, a mischievous smile pulling his lips upward as he spoke.

"So as long as you don't betray me, my lance surely won't pierce you." His teeth were so sharp...

"A-ah, well you won't have to worry about me betraying you because I don't exactly want to be skewered..." That smile of his never left his face as he chuckled, bringing a small blush to your cheeks.

"Then be glad, Master. You'll live to see yet another day."

"R-right.." 

Should you be glad or scared? You couldn't tell, but he was definitely trying to embarrass you.

**Bond Level: 5**

* * *

A few months later and you were starting to get along with Cu Alter, surprisingly enough. He accompanied you in most of your battles and also started walking you back to your room for the night, claiming that you 'would be of no use to anyone if you weren't well-rested'.

Cu was with you tonight as well. You made pleasant conversation with him as he walked by your side, pace slower than usual.

“If you’ve stuck with me this far, you should have a pretty good grasp of how I act, hm?”

"I think so… You're not as bad the others make you out to be, you know? I'm glad we're friends now, Cu." The Mad King grunted, but you couldn't tell if he was agreeing with you or not.

"That may be the case, but I am still your lance. Don't forget, Master." You both stopped in front of your bedroom door, and you were a bit unsure if you should send him away or invite him inside.

It was fairly late… But Cu beat you to the punch and spoke up first.

"Get some sleep, Master. I'll need you at peak performance tomorrow."

"O-of course... Good night, Cu."

Dammit.. You missed your chance.

**Bond Level: 6**

* * *

"By the way, I found this lying around. You can have it. Hold your hand out." You felt like he was addressing a child, but you showed him your hand regardless. Cu dropped something shiny in your hand that made you do a double-take from the object to your Servant’s nonchalant expression.

 _"Saint Quartz?!_ And you just found this lying around?" You asked incredulously, pleasantly surprised at your Berserker's gift; even if it was only one.

“...Yep.” It was a bit difficult to believe he just found this sitting on the floor somewhere random, but you chose not to question it further. After all, thanks were in order.

“Thank you so much, Cu!” Without much thought, you stood on the tip of your toes and pressed your lips against his cheek. He was surprisingly warm.

“It’s nothing...” When you pulled away, you could tell Cu was stunned, but his hood was casting a shadow over his face and you couldn’t tell if he was flustered or not.

“Come on, let’s go hang out in my room.” Your Servant grunted and followed behind you like a huge, intimidating puppy, glaring at any other Servants who tried to talk to you. It was actually kind of cute.

**Bond Level: 7**

* * *

“Master, why did you kiss my cheek the other day?” You looked up from the boring word search you were doing, lying on your stomach on his bed, feet kicking in the air. He was watching you curiously, seated a few feet away from you.

“I wanted to show my gratitude. Sorry, did I catch you off guard?” You asked with a teasing lilt to your voice, but Cu didn’t seem to mind that.

“Do you show your gratitude to all your Servants this way?” Was he asking if you kissed all your Servants?

“I-I mean, sometimes.. I hug some of my Servants as well, but I don’t kiss them in intimate ways if that’s what you’re wondering about.” Berserker appeared to be quite interested in whatever you were saying, but your focus was on your word search; just to avoid his scrutinizing gaze.

“How would you kiss someone in an intimate way, Master?” You nearly choked on your own spit, eyes finally snapping up to meet his own. He was staring at you intently.

“Uh, well I’d just k-kiss them on the lips?” Your Servant hummed thoughtfully before he leaned down until you were both face to face. Your eyes flickered back and forth between his lips and his eyes, unsure of where you should be looking.

“Have you kissed any of my.. Other selves on the lips before?” You shook your head, afraid your voice would sound far too meek if you spoke now.

“Good.” It was all too sudden for you, his closeness and then his lips brushing against yours. You were starting to feel lightheaded.

He cupped your cheek as his lips pressed against yours with an air of desperation behind his actions. You mewled when his tongue prodded against your bottom lip, wordlessly asking for permission.

Your lips parted and allowed his tongue inside, you didn’t even have to think about it. For Cu, your taste was indescribably sweet, more than likely due to all the coffee and sweets you consumed.

What felt like hours had only been a mere ten seconds before he pulled away, leaving your lips with a small nibble. You offered a small moan in response to being bitten, eyes half-lidded and cloudy with desire as your brain attempted to process everything that had just happened. But all you could think about was _Cu, Cu, Cu…_

“This is now my preferred method of showing gratitude.. For you only, of course, Master." He licked his lips slowly and you nearly passed out.

"I-I.. I'm glad to hear that, Cu."

**Bond Level: 8**

* * *

Considering you decided to take the day off just to relax, Cu Alter stayed with you inside your room for majority of the day as well. You were both discussing trivial matters when Cu asked you to close your eyes.

"Cup your hands together and hold them out." Feeling positively excited, you did as instructed and held your hands out with your eyes shut tight.

A few objects were dropped into your hands and you could immediately guess what they were. You opened your eyes to confirm what you felt against your palms, and you were even happier to find out your assumptions had been correct. _Three Saint Quartz?!_

"Do whatever you want with 'em. They're for you, after all..." You thanked him continuously while you stood up to store the quartz away for later. Before you could turn back around to thank Cu once again, you felt his arms wrap around your waist.

You turned around in his arms until you were staring up into those intimidating eyes of his, which were following every movement you made.

"I believe thanks are in order, Master." He wanted a kiss?

"I agree completely. Come here." With a crooked finger, you beckoned your Berserker to come closer and met his lips half way, noses brushing against one another.

It felt even better than the first kiss you shared together. Cu was much more controlling this time, immediately taking the initiative to press his lips harder against yours. He moved against you fiercely and desperately, forcing you to keep up with his pace.

He swallowed down each and every one of your whimpers and moans, mouth opening slightly as his tongue trailed across your lips. You let him in without much thought, moaning softly when you felt his tongue slipping further inside your mouth.

Cu's grip around your waist tightened the longer you kissed, causing your chests to push against one another's. Your knees nearly gave up when both of his hands reached down to grope your ass, squeezing harshly until you gasped loudly, muffled by his lips.

Alter pulled back for a few seconds, allowing you some time to breathe before his teeth were nipping at your bottom lip, forcing a whine from your throat. His hands were still squeezing your ass, even harder when you ran your nails down his bare chest; a low growl rumbling his chest.

"Tread carefully, Master. You have no idea what you're getting yourself into." Cu slowly retracted his arms from around your waist, hands grabbing both of yours gently with his own. You could feel his warmth.

"You should get some rest. I'll be here when you wake up." He could see the disappointed look on your flustered face, but Cu figured it was for the best. After all, he didn't think he would be able to hold back if you two went any further right now.

"Okay... Good night, Cu."

**Bond Level: 9**

* * *

Ever since Cu and you first made out, he was avid about doing it more and more often. Not that you were complaining, of course. You just didn't want any of the other Cu's to feel some type of way, if they saw you and Berserker sucking face like that. Not to mention, he had started biting your neck now.

Even still, Alter didn't seem to mind anyone seeing you two at all. If anything, he _wanted_ them to see him kissing their Master. Their beautiful, unobtainable Master was now his and there wasn't much anyone else could do about it.

Today, you were having a cup of coffee with Dr. Romani and chatting idly with da Vinci when Merlin noticed something on your neck.

"When had you been injured, Master? It looks fresh, but you haven't been in any battles as of late. Are you alright?" Cautiously, your fingers trailed up to your neck only to find a slight stinging pain whenever you pressed your nails against it. It was a bite mark…

"It doesn't appear to be life-threatening." Romani added in as he looked closer at the mark, until you covered it with your palm. Merlin eyed you suspiciously, lips upturned as if he knew _all_ of your dirty little secrets.

"I-I'm fine! I'll see you all later, I need to rethink a few battle plans!" Hurriedly, you excused yourself and took off down the hallway. You didn't stop until you were safe behind your door.

With a few heavy pants, you slumped against the door with your back to it. You suddenly didn't have any energy to do anything but cower in your room all day. One of your Servants had seen the bite mark on your neck, left by Berserker of course, and it just _had_ to be Merlin! Of all the Servants you summoned!

It wasn't as if Merlin was the gossiping type, he was just extremely bad at keeping his mouth shut sometimes. Especially when an opportunity to tease his Master arrived.

"Oi. Open the door." You scooted far enough away so the door wouldn't hit you as it opened, hands still against your face. Cu peeked his head inside first, looking for you around the room, only to find you sitting on the floor of all places. With your hands against your face.

Had you been crying? Your Servant crouched down to your level, and tapped your shoulder. You looked up at him, face extremely flushed but at least there were no tears yet.

"I'm assuming something is wrong. So talk."

"I d-didn't realize you left a mark.. And someone saw." Cu didn't appear to be concerned at all. If that self-satisfied grin on his face was anything to go by.

"Well, you _are_ mine now. I need to let the others know." You shook your head furiously before pressing your hands against your face again, suddenly feeling even hotter than before.

"I don't want anyone to find out and start spreading rumors! I wanted us to be official first…" The last part of your sentence was whispered, mostly to yourself, but he heard you loud and clear.

"...You want me to ask you out." It was more of a statement rather than a question, yet it made you giddy all the same. You nod slowly.

"Right... I forgot that was something humans did. I figured my actions were enough, but I suppose not. Master, be mine." Cu's unusual rendition of asking someone out actually made you giggle, and his eyes narrowed momentarily as if you had offended him.

Until you met his eyes. There were a few tears running down your cheeks, but you looked to be everything but sorrowful.

"Yes, Cu. I'll be yours if you'll be mine." You fell against his chest, snuggling closer to his warmth as his arms wrapped securely around you. You felt safe... Shielded.

"Foolish Master.. I was yours the moment you summoned me."

**Notes for the Chapter:**

> Full on smut mode in the next chapter, fellas!
> 
> Feedback, comments and kudos are, as always, much appreciated!  
> ♡(●´ω｀●)
> 
> My Tumblr: peachi-kun
> 
> Aesthetic Tumblr (NSFW): peechi-chan


	2. Bond 10

**Summary for the Chapter:**

> You reach Bond 10 with your Berserker.

**Notes for the Chapter:**

> ★ Hhhh, I wanted to post this sooner but I've had so many good ideas as of late! It's a bit difficult, debating on which ones to post first, yada yada, you guys don't care XD
> 
> ☆ Just enjoy the smut, please! I'll try to post more often since I'm done with my astronomy assignments for the time being! .3.

**Bond Level: 10**

* * *

How many times had it been today?

Two, three or maybe even five?

Your Berserker was being absolutely selfish and keeping you to himself, fucking you ever since the sun rose. Most of it happened in your bedroom, but it wasn’t as if he could stop himself from pulling you aside after a mission; just to make sure his scent was all over you. It was only slightly embarrassing, especially when your other Cu’s could _smell_ him on you.

But Alter wasn’t bothered in the slightest. If anything, he wanted those other dogs to see you were now taken; that you belonged to him. You had spent so much time trying to bond with him and now… This was your reward, unshakable loyalty in yet another Celtic warrior, regardless of his prior misconduct.

Currently, you were in bed attempting to relax after clearing a Singularity when your beloved Berserker decided to pay you yet another visit, not that you could complain. Your muscles were a bit tense, but Cu didn’t seem to mind that at all.

His hulking form towered over your own, one of his hands were big enough to hold both of your wrists loosely behind your back, whilst the other gripped at your hair.

A light tug was all it took before your head was tilted backwards, far enough to view the obscene display of your Berserker’s thick cock pushing inside you for what seemed like the tenth time today. At this point, your cunt was so wet there was little to no effort when he pushed deeper inside you.

“C-Cu! Fuck, I...” Your exhaustion-riddled mind could barely process any coherent thoughts right now, let alone form a full sentence.

By merely shifting his hips, half of his length was inside, stretching you out deliciously. Your muscles were beginning to loosen up now, that much was obvious. However, you could barely feel your legs anymore.

Even more exhausted now, your chest fell against the bed and your ass pushed back against him. Cu let go of your hair, allowing you to slouch on the bed with your cheek resting against it with a few small pants.

“For someone who complains a lot about others not seeing or hearing us, you sure are noisy.” He was teasing you of course, if that self-satisfied smirk of his was anything to go by. Cu couldn’t care less who heard.

After having you so many times today, Cu was anything but gentle, pounding into you like the beast he was until your body started trembling. A shrill squeak came tumbling from your lips when you felt his cock swelling inside your womb, the feeling all too familiar after you’ve experienced it for most of the day.

You still wanted to cum, no matter how tired you were. Your Berserker could tell you wouldn't last much longer from the way your thighs were trembling insistently, short screams of pleasure forcing their way out of you. Cu was ready for you to receive his knot… Again.

“F-fuck, Cu! Inside, plea- _ahh!_ I n-need it inside!” You could feel his chest rumbling with laughter. As if he would cum anywhere else _but_ inside his Master's pretty little cunt. It was his now, after all.

Despite the fact that Cu was doing literally all of the work, you were still covered in a thin layer of sweat, drool running down the underside of your neck. But he hadn’t even broken a sweat. Should you be envious? Probably.

To keep you from squirming away, that long tail of his wrapped around your midsection firmly and held you in place. You were a bit afraid of being impaled by the spikes covering it until you realized that there weren’t any; much to your surprise. He must have retracted them for your sake. That alone was enough to bring a tired smile to your lips.

“Come here.” Your body was a bit sluggish as Cu changed positions, moving so that you were now in his lap and facing him.

You wrapped your arms around his neck instinctively, whimpering slightly as that monstrous cock of his pushed back inside you until you were flush with one another. Squelching sounds resonated in your ears, enough to make you flustered and embarrassed at how wet you were. Your Berserker chuckled as you buried your face in his chest.

“Are you actually getting shy on me now?” You shook your head defiantly, face still hidden.

“Good. Because I’m not finished with you.” Even after everything today, you couldn’t say you were exactly surprised that your Berserker still wasn’t satisfied.

He had never been easy to appease, whether it be in battle or the bedroom. With his nose buried in your hair, his hips snapped up into yours until it hurt but you knew better than to try to move or get away. With a pained moan, your arms tightened around his neck.

You could feel the base of his cock beginning to swell and it brought another strangled moan from your mouth, head spinning until you had to shut your eyes to keep from passing out or feeling extremely dazed.

“You gonna make me do all the work again?” Cu asked teasingly, referring to your sleepy expression. You were about ready to fall asleep, even as you received his knot, you felt your lower half beginning to thrum with pain.

Not a single drop of his warm seed went to waste, as usual, you could feel the tip twitching violently as Cu pumped your womb with more and more cum. You would be stuck together for a bit, but you didn’t exactly mind. What you _did_ mind was cleaning up when he was finally able to pull out...

“Will you stay with me, Cu?” He snorted, trying not to bark out a laugh when you were so close to sleeping.

“I don’t exactly have a choice, Master. Now go to sleep.” With a cute little yawn, you snuggled further into his chest and mumbled, “I love you” before falling asleep.

“...I love you too.”

**Notes for the Chapter:**

> Feedback, comments and kudos are, as always, much appreciated!  
> ♡(●´ω｀●)
> 
> My Tumblr: peachi-kun
> 
> Aesthetic Tumblr (NSFW): peechi-chan


End file.
